1. Field of the Invention
The present invention relates to a space system including a single assist module coupled to a plurality of space-vehicles or spacecraft, and more particularly to a method of launching the single assist module together with the plurality of spacecraft and then controllably guiding the spacecraft into different desired orbits, such as interplanetary orbits, individually.
2. Description of the Background Art
A problem to be solved by the present invention is a difficulty in, after launching a plurality of spacecraft all together, injection them into different orbits, such as circum-earth orbits or interplanetary orbits, individually. A conventional solution of this problem has involved the need for equipping each of the spacecraft with its own rocket (launch vehicle), and inevitably led to significant increase in cost. Particularly, in an operation for injection a plurality small-size spacecraft into a variety of different orbits individually, it has been essentially required to equip each of the spacecraft with its own launching means. Thus, such an operation has been regarded as unrealizable because of extremely poor efficiency and unacceptable cost performance.
Japanese Patent Laid-Open Publication No. 07-187091 (Patent Publication 1) discloses a method of launching a plurality of space satellites, particularly, a technique of reducing a fuel consumption in an orbit-control propulsion system (orbital maneuvering system) for orbital transfer.
In this technique disclosed in the Patent Publication 1, two satellites S1, S2 mounted on a single common rocket and launched simultaneously are injected into a parking orbit P having a semi-major axis length less than those of first and second target orbits A1, A2. Then, when the parking orbit P comes close to being in plane with the first target orbit A1, an in-plane orbit control is performed using a propulsion system for the first satellite S1 to move the first satellite S1 to the first target orbits A1 via a transfer orbit A1′ to the first target orbits A1. Then, in the same manner, when the parking orbit P comes close to being in plane with the second target orbit A2, the second satellite S2 is moved to the second target orbits A2 via a transfer orbit A2′ to the second target orbits A2.
Fundamentally, the technique disclosed in the Patent Publication 1 is not designed to change an inclination of a circum-earth orbit. In contrast, the present invention is premised on a system capable of changing an orbital element by means of a perturbation effect arising from a gravitational field of the earth.
In addition to the above problem in principle about incapability of maneuvering an inclination of an established orbit, the technique disclosed in the Patent Publication 1 is not originally designed to inject a plurality of spacecraft into different interplanetary orbits individually.